Polishing apparatus and polishing method

ABSTRACT

A polishing apparatus comprises a first polishing table having a first polishing surface, a substrate carrier for holding a substrate and positioning the substrate so as to bring a surface of the substrate into contact with the first polishing surface, a pressing mechanism for pressing, against the first polishing surface, the surface of the substrate which has been brought into contact with the first polishing surface by the substrate carrier, a retainer ring mounted on the substrate carrier so as to surround the substrate which has been pressed against the first polishing surface by the pressing mechanism, and a retainer-ring-position-adjustment mechanism for adjustably positioning the retainer ring relative to the substrate, which has been pressed against the first polishing surface, in directions toward and away from the first polishing surface.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an apparatus for performingplanarization polishing of a substrate, and in particular to anapparatus for performing, chemical-mechanical polishing of a substratesuch as a semiconductor wafer, for planarizing the substrate.

[0003] 2. Background Art

[0004] In earlier polishing apparatus, a substrate to be polished washeld on the lower surface of a substrate carrier. Then, to polish thesubstrate, it was pressed against a polishing pad as a polishing slurrywas supplied to the polishing surface of the pad, while establishing arelative motion between the substrate and the polishing pad. Thesubstrate carrier was provided with a retainer ring to prevent thesubstrate from being dislodged from the lower surface of the substratecarrier during polishing. The substrate was surrounded by the retainingring to hold it in place on the carrier

[0005] During polishing performed on the resilient polishing pad,however, excessive polishing occurred at the periphery of the workpiece,producing an effect referred to as ‘edge rounding.’ To suppress thisedge rounding effect, the retainer ring was pressed against thepolishing pad to flex it slightly downward at its periphery.

[0006] In conventional polishing apparatus such as described above,although pressing the retainer ring against the polishing pad solved theedge rounding problem, thus improving the surface finish precision ofthe polished workpiece, it also resulted in poor distribution of slurryover the surface of the workpiece being polished, which reducedpolishing speed, thereby degrading productivity. This tendency wasespecially pronounced when the surface being polished was a metal film.Consequently, this conventional polishing apparatus was poorly suitedfor high-speed polishing, which requires that a large amount of slurrybe supplied to the surface being polished.

[0007] Recently, polishing apparatuses that use a fixed abrasive insteadof a polishing pad have been developed. Because a fixed abrasiveexperiences almost no shape deformation when a workpiece is pressedagainst it, it produces very little edge rounding, even in the absenceof downward pressure from a retainer ring. When such a fixed abrasive isused for polishing in a conventional polishing apparatus, however,because the retainer ring is now being pressed against a fixed abrasive,the ring wears faster, and the shorter retainer ring service life causesa corresponding increase in cost.

BRIEF SUMMARY OF THE INVENTION

[0008] It is therefore an object of the present invention to provide apolishing apparatus and method capable of performing polishing such thatedge rounding is eliminated, thus improving the finish precision of thepolished workpiece; and such that a large amount of polishing solutioncan be supplied to the surface being polished, thereby increasingpolishing speed and improving productivity.

[0009] To accomplish the above object, according to a first aspect ofthe present invention, a polishing apparatus 1, as shown for example inFIGS. 1 and 2, comprises a substrate carrier 10 having a retainer ring 3that surrounds a substrate S for retaining the substrate S; a polishingtool 15, for polishing the substrate S; a substrate-pressing mechanism11, for bringing a substrate S into contact with a polishing surface 17of the polishing tool 15; a retainer-ring-pressing mechanism 16 forbringing the retainer ring 3 into contact with the polishing surface 17;and a retainer-ring-position-adjustment mechanism 4, for adjusting thepositional relationship between the retainer ring 3 and the polishingsurface 17 such that a gap is formed therebetween when the substrate Sis brought into contact with the polishing surface 17.

[0010] This configuration has a retainer-ring-pressing mechanism 16 forpressing the retainer ring 3 against the polishing surface 17. Thisprevents the forming of an ‘edge rounding’ on the polished substratesurface SA when it is polished by the polishing surface 17, therebyimproving the surface finish precision of the polished substrate S. Theconfiguration also includes a retainer-ring-position-adjustmentmechanism 4. When necessary, this retainer-ring-position-adjustmentmechanism 4 can used to adjust the positional relationship between theretainer ring 3 and the polishing surface 17 such that when thesubstrate S is pressed against the polishing surface 17, a gap will beformed between the retainer ring 3 and the polishing surface 17. Whenthis is done, the lack of physical contact between the retainer ring 3and the polishing surface 17 increases the polishing speed (polishingrate), thus improving polishing productivity.

[0011] Also, according to a second aspect of the present invention, thepolishing apparatus 1 of the first aspect thereof adds two sensors (18and 19) for sensing the amount of polishing of the substrate S by thepolishing tool 15. This enables the apparatus to switch back and forthbetween a mode in which polishing is performed with the retainer ring 3being pressed against the polishing surface 17 by theretainer-ring-pressing mechanism 16, and a mode in which polishing isperformed with no contact between the retainer ring 3 and the polishingsurface 17, thus to perform appropriate polishing based on the amount ofpolishing already performed, as sensed by the sensors (18 and 19).

[0012] Also, a polishing method for accomplishing the above objectaccording to a third aspect of the present invention, as shown forexample in FIGS. 1 and 2, comprises a first step of holding thesubstrate S in the substrate carrier 10 surrounded by the retainer ring3; a second step of bringing the substrate S into contact with thepolishing surface 17 while adjusting the positional relationship betweenthe retainer ring 3 and the polishing surface 17 such that a gap isformed therebetween, and also effecting relative motion between thesubstrate S and the polishing surface 17, for performing polishing; anda third step of bringing the substrate S into contact with the polishingsurface 17 while pressing the retainer ring 3 into contact with thepolishing surface 17, and also effecting relative motion between thesubstrate S and the polishing surface 17, for performing polishing.

[0013] Also, a polishing method according to a fourth aspect of thepresent invention is the method of the above third aspect wherein thepolishing surface 17 of the second step is a fixed abrasive 15B; and thepolishing surface 17 of the third step is a polishing pad 15A.

[0014] Moreover, a polishing method according to a fifth aspect of thepresent invention is the method of the third or fourth aspect wherein atleast one of the second and third steps includes a fourth step ofmeasuring the amount of polishing, and wherein the process proceeds fromthe fourth step to the other of the second and third steps after theamount of polishing reaches a prescribed value.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0015] These and other features, aspects, and advantages of the presentinvention will become apparent with reference to the followingdescription, claims, and accompanying drawings, where:

[0016]FIG. 1 shows an external view of the polishing apparatus in oneembodiment of the present invention;

[0017]FIG. 2 is an enlarged partial cross-section view of the polishingapparatus of FIG. 1, with its substrate carrier positioned directlyabove its turntable;

[0018]FIG. 3 is a plan view of a substrate that is retained in

[0019] the substrate carrier of the polishing apparatus of FIG. 1;

[0020]FIG. 4(A) shows a typical cross-section of substrate havingportions to be polished that include a film of one metal, and a film ofanother metal sandwiched between films of the first metal. FIG. 4(B)shows a typical cross-section of a substrate made up of one metal film,where that one film is to be polished;

[0021]FIG. 5 shows an external view of the polishing apparatus inanother embodiment of the present invention;

[0022]FIG. 6 shows an external view of the polishing apparatus in yetanother embodiment of the present invention;

[0023]FIG. 7 is an enlarged partial cross-section view of the polishingapparatus in a further embodiment of the present invention.

DETAILED DESCRIPTION

[0024] The best mode for implementing the present invention is describedbelow, with reference to the drawings. For the purposes of thisdescription, when the same item or an equivalent item appears in morethan one figure, it is assigned the same number in all drawings in whichit appears, and the description of that item is not repeated.

[0025]FIG. 1 shows an exterior view of a polishing apparatus 1 in thisembodiment of the present invention. The configuration of this polishingapparatus will now be described, with reference to FIG. 1.

[0026] The polishing apparatus 1 comprises a substrate carrier 10 forholding a substrate S, a carrier drive shaft 12 for driving thesubstrate carrier 10 in rotation, a carrier head 13 that supports thecarrier drive shaft 12 and a pivotal shaft 14. The pivotal shaft 14pivots with its own axis as the center of motion, thereby causing asimilar pivoting of the carrier head 13 and substrate carrier 10.

[0027] The polishing apparatus 1 also comprises a polishing table 36,which has a polishing tool 15 attached to it; and a rotary transporter27 for transporting items between a lifter 29 and a pusher 30 (both tobe described later). The polishing tool 15 has a polishing pad 1SA and afixed abrasive 15B. The polishing table 36 has a turntable 36A, to whichthe polishing pad 15A is attached; and a scroll table 36B, to which thefixed abrasive 15B is attached. The polishing surface 17 of thepolishing tool 15 is constituted of a polishing surface 17A of thepolishing pad 15A, and a polishing surface 17B of the fixed abrasive15B.

[0028] During polishing, purified water, a slurry, or a chemicalsolution (or a combination of these) can be supplied to the turntable36A and scroll table 36B as a polishing solution. The substrate carrier10 can be positioned directly above the turntable 36A, the scroll table36B, or a pusher 30 (to be described later), by pivoting the pivotalshaft 14. The pivotal shaft 14 has a positioning mechanism (not shown inthe drawing) through which the substrate carrier 10 can be pivotallypositioned.

[0029] The polishing apparatus 1 also comprises a substrate inverter 28for turning over a substrate S; a lifter 29 for transporting thesubstrate S between the substrate inverter 28 and the rotary transporter27; a pusher 30 for accepting a substrate S transported by the rotarytransporter 27 and transferring it to the substrate carrier 10; a firstdresser 20 for dressing the polishing pad 15A of the turntable 36A, anda second dresser 50 for dressing the fixed abrasive 15B of the scrolltable 36B.

[0030] The substrate carrier 10 will be described with reference to FIG.2. The substrate carrier 10 has a cylindrical-container-like substratecarrier main unit 2 that has an internal containment space; and aretainer ring 3 that is installed on the bottom of the substrate carriermain unit 2 so as to form a single unit therewith. Enclosed within aspace defined by the inside of the substrate carrier main unit 2 and theretainer ring 3, are a seal ring 42 that touches the top of a substrateS, a ring-shaped holder ring 5, and an approximatelycircular-disk-shaped chucking plate 6 for holding the seal ring 42. Thelower surface of the substrate S is the to-be-polished substrate surfaceSA.

[0031] The seal ring 42, which is made of a resilient film, has itsouter periphery clamped between the holder ring 5 and the chucking plate6 (which is fastened to the bottom of the holder ring 5) such that itcovers the outer edge of the top surface, outer side portion, and outeredge of the bottom surface, of the chucking plate 6. This results in aspace G being formed between the seal ring 42 and the chucking plate 6.During polishing, the seal ring 42 adheres tightly to the top surface ofthe substrate S, sealing the space G.

[0032] A pressure sheet 7 made of a resilient film is stretched betweenthe holder ring 5 and the substrate carrier main unit 2. This pressuresheet 7 is secured by having its outer peripheral edge portion clampedbetween a housing 2A of the substrate carrier main unit 2 and a pressuresheet support 2B, and its inner peripheral edge portion clamped betweenthe top SA and stopper 5B of the holder ring 5. The substrate carriermain unit 2, chucking plate 6, holder ring 5, and pressure sheet 7combine to form a pressure chamber 21 inside the substrate carrier mainunit 2.

[0033] A fluid path 31, made up of tubing, connectors, etc.,communicates with the pressure chamber 21, which is connected to acompressed air supply (not illustrated) through a regulator R1 locatedin the fluid path 31.

[0034] Provided within a space formed between the substrate S and thechucking plate 6 are a center bag 8 and a ring tube 9 that make contactwith the substrate S. The center bag 8, which has a circular contactsurface, is placed in the center of the bottom surface of the chuckingplate 6; and the ring tube 9, which has a ring-shaped contact surface,is placed outward of the center bag 8, surrounding its periphery.

[0035] The space formed between the chucking plate 6 and the substrate Sis partitioned into multiple spaces by the center bag 8 and ring tube 9:That is, a pressure chamber 22 is formed between the center bag 8 andring tube 9, and a pressure chamber 23 is formed outward of the ringtube 9. Inside the center bag 8, a central pressure chamber (alsoreferred to as simply a pressure chamber) 24 is formed by a resilientfilm 81 and a center bag holder 82. Inside the ring tube 9, anintermediate pressure chamber (also referred to as simply a pressurechamber) 25 is formed by a resilient film 91 and a ring tube holder 92.

[0036] Fluid paths 32, 33, 34, and 35, respectively, made up of tubing,connectors, etc., communicate with the pressures chamber 22 and 23, thecentral pressure chamber 24, and the intermediate pressure chamber 25.The pressure chambers 22, 23, 24, and 25 are connected to a compressedair supply (not illustrated), as a supply source, through regulators R2,R3, R4, and R5, respectively, which are placed in the fluid paths 32,33, 34, and 35, respectively.

[0037] The system is configured so that a fluid such as air, eitherpressurized or at atmospheric pressure, can be supplied to the pressurechamber 21 above the chucking plate 6, as well as to the pressurechambers (22-25) through the fluid paths (31-35) in communication withtheir respective pressure chambers. The pressure of the pressurizationfluid supplied to each of the pressure chambers (21-25) can be adjustedby the regulator (R1-R5) located in the fluid path (31-35) for thatchamber. Thus the pressure in each of the chambers (21-25) can becontrolled independently of the others, or can be placed at atmosphericpressure. Making the pressures in the different pressure chambers(21-25) independently adjustable by the regulators (R1-R5) enables thepressing force with which the substrate S is pressed against thepolishing pad 15A to be adjusted separately for each part of thesubstrate S. Moreover, the pressure chambers 22 and 23 are configured tobe switchably connected to a vacuum source (not shown in the drawing) sothat the chambers 22 and 23 can be switched to a vacuum.

[0038] Because there is a slight gap H between the outer peripheralsurface of the seal ring 42 and the retainer ring 3, the configurationat this point constitutes a floating structure in which some components(such as the holder ring 5, the chucking plate 6, and the seal ring 42installed on the chucking plate 6) are movable vertically with respectto the substrate carrier main unit 2 and the retainer ring 3. Also,provided, at a number of locations on the stopper 5B of the holder ring5, protruding outward from the periphery thereof, are a plurality ofprotrusions 5C. The vertical travel of the movable components (holderring 5, etc.) is limited to a given point by the engagement of theseprotrusions 5C with the upper surface 3B of a portion 3A of the retainerring 3 that protrudes inward from the retainer ring 3.

[0039] The regulators R1-R5, the fluid paths 31-35, the pressurechambers 21-25, and the chucking plate 6 are all part of thesubstrate-pressing mechanism 11.

[0040] Next, the mechanisms for rotating the substrate carrier 10 andmoving it up and down will be described. The substrate carrier 10 isconnected through a gimbal mechanism 52 to a load cell 51 installed atthe lower end of the substrate carrier drive shaft 12.

[0041] The substrate carrier drive shaft 12 is positioned vertically inthe apparatus, inserted in a spline bearing 53, which is in turninserted in a pulley 54. The pulley 54 is rotatably installed in theinner cavity 56A of a support unit 56 in which it is housed. Thevertically oriented substrate carrier drive shaft 12 passes through thehorizontally oriented support unit 56. A drive means (not shown in thedrawing) drives the substrate carrier drive shaft 12 through a timingbelt 55 (indicated by phantom lines in the drawing) wrapped around thepulley 54. The timing belt 55 runs inside the inner cavity 56A.

[0042] Installed above the support unit 56 is a pulse motor 57 coupledto one end of a ball screw 58. The ball screw 58 is threaded into a ballnut 59 that is coupled to the top end of the substrate carrier driveshaft 12. Thus by operating the pulse motor 57, the substrate carrier 10and its connected substrate carrier drive shaft 12 can be raised orlowered as a single unit, and stopped at the desired height. A steppingmotor or servo motor can be used for the pulse motor 57.

[0043] Note that while not shown in FIG. 2 (see FIG. 1) the portionabove and including the support unit 56 is housed within the carrierhead 13. Also, a portion of the substrate carrier drive shaft 12extending downward below the support unit 56, the load cell 51, and aportion of the gimbal mechanism 52, are enclosed within moisturebarriers 60A and 60B. This is not shown in FIG. 1.

[0044] Provided as a sensor mechanism on the turntable 36A is a firstend-point sensor mechanism 18, and provided as a sensor mechanism on thescroll table 36B is a second end-point sensor mechanism 19. The firstand second end-point sensor mechanisms 18 and 19 detect the fact thatthe polishing of a substrate S has progressed to a prescribed value(end-point), at which point they output a detect signal to a controlmechanism (not shown). The sensors used for the first and secondend-point sensor mechanisms 18 and 19 may be either optical- orover-current-type sensors. If a polishing torque sensor for sensingpolishing torque (not shown in the drawings) is provided in thepolishing apparatus 1, for determining the amount of polishing based onthe sensed polishing torque value, end-point sensor mechanisms need notbe provided on the tables per-se.

[0045] The pulse motor 57, ball screw 58, ball nut 59, load cell 51 andsubstrate carrier drive shaft 12 are all included in theretainer-ring-position-adjustment mechanism 4. Also, the pulse motor 57,ball screw 58, ball nut 59, load cell 51, and substrate carrier driveshaft 12 are included in the retainer-ring-pressing mechanism 16configuration.

[0046] The operation of the substrate carrier 10 of the polishingapparatus 1 in one embodiment of the present invention will now bedescribed with reference to FIG. 2, and when appropriate, to FIGS. 1 and3. In the polishing apparatus 1 of the present embodiment, to acquireand retain a substrate S in the substrate carrier 10, the entiresubstrate carrier 10 is first positioned directly over the substrate S.A pressurization fluid is then supplied to the center bag 8 and thepressure chambers 24 and 25 (inside the ring tube 9), to pressurize themto the prescribed pressure. Then, a pulse signal is transmitted from acontrol mechanism (not shown) to the pulse motor 57, to lower thesubstrate carrier 10. In response, the pulse motor 57 rotates the ballscrew 58, driving it into the ball nut 59, causing the substrate carrierdrive shaft 12 to descend, thus lowering the substrate carrier 10 untilthe bottom surfaces of the center bag 8 and ring tube 9 make a tightseal with substrate S to be held.

[0047] Next, the pressure chambers 22 and 23 are connected through thefluid paths 32 and 33, respectively, to a source of vacuum (not shown)to obtain negative pressures in the pressure chambers 22 and 23, thus tocreate the suction required to hold the substrate S by suction-adhesion.The control mechanism (not shown in the drawing) then transmits a pulsesignal to the pulse motor 57 to raise the substrate carrier 10 with thesubstrate S held fast therein by suction. The pulse motor 57 operates(through the ball screw 58, ball nut 59, and substrate carrier driveshaft 12) similarly to the operation described above for lowering, butrotating in the opposite direction. Next, the pivotal shaft 14 ispivoted to shift the entire substrate carrier 10 as required to positionit directly over the turntable 36A and its polishing pad 15A. Also, theperiphery of the substrate S is held by the retainer ring 3 to preventit from being dislodged from the substrate carrier 10 during polishing.

[0048] Next, the substrate carrier 10 is lowered to bring the surface ofthe substrate S to be polished, and the lower surface of the retainerring 3, into contact with the polishing pad 15A. When the substrate Sand the retainer ring 3 come into contact with the polishing surface17A, this applies a load to the load cell 51 installed on the lower endof the substrate carrier drive shaft 12. The load cell 51 detects theload and sends a ‘load detect’ signal to the control mechanism (notshown), which then recognizes that the substrate S and retainer ring 3have been brought into contact with the polishing pad 15A.

[0049] The control mechanism then sends pulse signals to the pulse motor57 so that the pulse motor rotates to raise the substrate carrier 10 tothe prescribed position. This makes it possible to keep the positions ofthe polishing pad 15A and retainer ring 3 the same, regardless ofretainer ring 3 wear. Specifically the substrate carrier 10 is raisedapproximately 0.2 mm, but because the substrate S is approximately 0.8mm thick, it cannot be thrown from the bottom of the substrate carrier10 during polishing.

[0050] With the apparatus in this state, pressurization fluid issupplied to the pressure chambers 21-23 at a prescribed pressure, topress the substrate S against the polishing surface 17A on the turntable36A. Polishing solution is caused to flow from a polishing solutionsupply nozzle (not shown) so as to maintain a sufficient quantity ofpolishing solution on the polishing pad 15A to ensure that polishing isalways performed with polishing solution present between theto-be-polished substrate surface SA and the polishing surface 17A of thepolishing pad 15A.

[0051] At this stage (see FIG. 3), the portions C2 and C4 of thesubstrate S (the portions positioned under the pressure chambers 22 and23) are pressed against the polishing surface 17A by fluid pressuressupplied to the pressure chambers 22 and 23, respectively. Similarly,the portion C1 of the substrate S, which is positioned under the centralpressure chamber 24, is pressed against the polishing pad 15A bypressurization fluid pressure, which is applied to the central pressurechamber 24 via the resilient film 81 of the center bag 8. The portion C3of the substrate S, which is positioned under the intermediate pressurechamber 25, is pressed against the polishing surface 17A bypressurization fluid pressure applied, through the resilient film 91 ofthe ring tube 9, to the intermediate pressure chamber 25. Further, theforce with which the substrate S is pressed against the polishingsurface 17A can be changed by supplying pressurization fluid to thepressure chamber 21, or changing the pressure of the pressurizationfluid.

[0052] Thus the polishing pressures applied to the substrate S can beadjusted by controlling the pressure of the pressurization fluidsupplied to each of the pressure chambers 21-25. That is, the force withwhich the substrate S is pressed against the polishing pad 15A on theturntable 36A can be adjusted independently for each of the individualportions C1-C4 of the substrate S. This is done by individuallyadjusting the regulators R1-R5 placed in the fluid paths 31-35,respectively, to thereby adjust the pressures of the pressurizationfluid supplied to the individual pressure chambers 21-25.

[0053] In this manner, the substrate S can be pressed against thepolishing pad 15A of the rotating turntable 36A with the polishingpressure applied to each of the portions C1-C4 of the substrate Sindividually adjusted to a desired value. By appropriately adjusting thepressing force used to press the substrate S against the polishing pad15A, the distribution of polishing pressure over the portions of thesubstrate S surface (the portion C1, positioned under the centralpressure chamber 24; the portion C2, positioned under the pressurechamber 22; the portion C3, positioned under the intermediate pressurechamber 25; and the portion C4, the pressure chamber 22 portion) can beadjusted as desired.

[0054] Thus the substrate S can be divided into four concentric circles(the circular portion Cl and the ring-shaped portions C2-C4) and each ofthese separate portions C1-C4 can be pressed with an independentlydefined pressing force. The polishing rate is dependent on the pressurewith which the substrate S is pressed against the polishing pad 15A, andbecause the pressure applied to each of the substrate S portions C1-C4can be adjusted as described above, the polishing rate can also beindependently controlled for the different sections of the four sectionsC1-C4. This makes it possible to obtain uniform polishing over theentire surface of the substrate S with no under-polishing orover-polishing, even when a thin film on a substrate S surface to bepolished has a radial film thickness distribution.

[0055] The substrate S can also be polished with the retainer ring 3 notin contact with the polishing surface 17A. This allows more polishingsolution to enter between the to-be-polished substrate surface SA of thesubstrate S and the polishing surface 17A than would be possible withthe retainer ring 3 in contact with the polishing surface 17A, therebyincreasing the polishing rate. In addition to increasing the polishingrate, the polishing with the retainer ring 3 not in contact with thepolishing surface also reduces retainer ring 3 wear, which dramaticallyextends retainer ring 3 service life.

[0056] To perform polishing with the retainer ring 3 in contact with thepolishing pad 15A, after the substrate carrier 10 has been loweredsufficiently to bring the substrate S and retainer ring 3 into contactwith the polishing pad 15A, the following operation is performed: Pulsesignals are sent from the controller (not shown) to the pulse motor 57,to cause the pulse motor 57 to rotate the ball screw 58, which operatesin cooperation with the ball nut 59 and substrate carrier drive shaft 12to further lower the substrate carrier 10 and thus press the retainerring 3 with an increasing force against the polishing pad 15A until theload cell 51 detects a load that corresponds to the retainer ringpressure specified in a pre-set polishing recipe.

[0057] Polishing pressure is controlled using feedback control. Thus,when the retainer ring 3 is pressed against the polishing pad 15A, thisapplies a load to the load cell 51, and when the load reaches aprescribed value a load signal is transmitted by the load cell 51 to thecontrol mechanism to stop rotation of the pulse motor 57. Then, asdescribed above, the substrate S is pressed against the polishing pad15A by pressurizing the pressure chambers 21-23; and if required,changing the pressures in the central and intermediate pressure chambers24 and 25; and the turntable 36A is rotated, to perform the polishingoperation.

[0058] When this is done, polishing pad ‘edge rounding’ problems thatoccur when polishing cloths such as ICI 1000/SUBA400 are used as thepolishing pad 15A, can be solved by controlling retainer ring pressure.This also improves uniformity within the substrate S surface, andincreases productivity.

[0059] Next, referring to the drawings, operation of the polishingapparatus 1 of the present embodiment will be described for a polishingprocess in which the retainer ring 3 is brought into contact with thepolishing surface 17, and a process in which it is not. For thisoperation, the polishing tools 15 used on the turntable 36A and scrolltable 36B are as described below.

[0060] A Polishing Procedure (1) will be described with reference toFIG. 2, and when applicable, to FIGS. 5 and 4A. In this procedure, ametal film 61 is polished first; then a rest of the metal film 61 and ametal film 62 are polished at the same time.

[0061] Here, as shown in FIG. 5, a polishing pad 15A is used on theturntable 36A, the same as in FIG. 1; but on the scroll table 36B, apolishing pad 115A (instead of a fixed abrasive 15B) is used as thepolishing tool. The polishing pad 115A has a polishing surface 117A.

[0062] A substrate S1, a cross-section of which is shown in FIG. 4(A),has a metal film 61, (of copper, etc.) formed by a process such aselectroplating, and a metal film 62 formed as a barrier layer under themetal film 61. Polishing of metal film 61 only is performed up to alevel designated as X1 in the drawing; then, from the X1 level to a Y1level, simultaneous polishing of the metal film 61 and the metal film 62is performed.

[0063] First, the substrate carrier head 13 is pivoted about the pivotalshaft 14 to position the substrate carrier 10 directly over the pusher30. Next, the pressure chambers 24 and 25 are pressurized, and thepusher 30 is raised until the substrate S1 to be polished is touchingthe bottom of the substrate carrier 10 (the seal ring 42 and theresilient films 81 and 82). Then, a negative pressure is obtained in thepressure chambers 22 and 23 to create suction to hold the substrate S1against the substrate carrier 10. At this point, the substrate S1 beingheld on the substrate carrier 10 is surrounded by the retainer ring 3.

[0064] Next, the substrate carrier 10 is positioned directly above theturntable 36A, after which the pulse motor 57 shaft is rotated to lowerthe substrate carrier 10 so as to bring the retainer ring 3 into contactwith the polishing pad 15A on the turntable 36A and press the substrateS1 against the polishing pad 15A. After the substrate carrier 10 touchesthe polishing pad 15A, however, the pulse motor 57 is reversed to raisethe substrate carrier 10 slightly (e.g. 0.2 mm), thus positioning theretainer ring 3 above the polishing pad 15A, to form a gap of theprescribed size between the bottom of the retainer ring 3 and thepolishing surface 17A of the polishing pad 15A.

[0065] Now, the pressure chambers 21-23 are pressurized, pressing thesubstrate S1 against the polishing pad 15A; and the turntable 36A isturned, effecting relative motion between the substrate S1 and thepolishing surface 17A; to polish the metal film 61. This technique(i.e., polishing with the retainer ring 3 not touching the polishingsurface 17A) improves the entry of polishing solution between theto-be-polished substrate surface SA1 of the substrate S1 and thepolishing surface 17A, which increases the polishing rate. Because thetechnique also reduces retainer ring 3 wear, it greatly extends theservice life of the retainer ring 3.

[0066] When the prescribed amount of polishing has been performed, andthe first end-point sensor mechanism 18 detects that the to-be-polishedsubstrate surface SA1 has reached the X1 level, the rotation of theturntable 36A is stopped. The pressure chamber 21 is now taken toatmospheric pressure, and the pressure chambers 22 and 23 are taken tonegative pressure, thus creating suction to cause the substrate S1 toadhere to the substrate carrier 10. The pulse motor 57 is now operatedto raise the substrate carrier 10, completing the polishing process onthe turntable 36A.

[0067] Next, the substrate carrier head 13 is pivoted about the pivotalshaft 14 to position the substrate carrier 10 directly over the scrolltable 36B. The substrate carrier 10 is now lowered, the pressurechambers 21-23 pressurized, and the to-be-polished substrate surface SA1pressed against the polishing pad 115A, to begin polishing. After thesubstrate carrier 10 makes contact with the polishing pad 115A, withoutraising the substrate carrier 10, the pulse motor 57 is rotated slowlyand the substrate carrier 10 lowered slightly, pressing the retainerring 3 against the polishing pad 115A, to polish the metal film 61 andmetal film 62. When polishing is performed in this manner, the polishingpad 115A experiences no “edge rounding” problem. This enables uniformpolishing up to the edge of the to-be-polished substrate surface SA1,thus enabling an increase in planarity.

[0068] When the prescribed amount of polishing has been performed: i.e.,when the to-be-polished substrate surface SA1 has reached the Y1 level;this is detected by the second end-point sensor mechanism 19, and thepolishing is stopped.

[0069] The pressure chamber 21 is then taken to atmospheric pressure,and the pressure chambers 22 and 23 to negative pressure, thus creatingsuction to hold the substrate S1 on the substrate carrier 10. Thesubstrate carrier 10 is then raised, ending the polishing process on thescroll table 36B. Next, the substrate carrier 10 is positioned directlyover the pusher 30, and the pusher 30 is raised to the substratetransfer position. The pressure chambers 22 and 23 are then returned toatmospheric pressure to release the substrate S1 from the substratecarrier 10 and transfer it to the pusher 30.

[0070] The above description of Polishing Procedure (1) describedpolishing a substrate S1 in which the portion to be polished comprised ametal film 61 and a metal film 62. However, the polishing of a substrateS2 in which the portion to be polished has only a metal film 61, asshown in FIG. 4B, may also be performed by first polishing as far as theX2 level, and then polishing to the Y2 level, following the samePolishing Procedure (1) for both portions. In such cases, the polishingrate for the portion prior to the X2 level can be increased, to improveproductivity; and polishing between the X2 and Y2 levels can beperformed to obtain the best possible surface planarity.

[0071] A Polishing Procedure (2) as used to polishing a metal film 61using a single polishing table 36, will now be described with referenceto FIG. 2, and when applicable, to FIG. 4(B). This example uses theturntable 36A shown in FIG. 2, with a polishing pad 15A used on theturntable 36A (FIG. 2). A substrate S2 as shown in FIG. 4(B) is used asthe substrate to be polished.

[0072] The following description describes only the portions of thisprocedure that are different from Polishing Procedure (1): Up to thelevel X2, polishing of the substrate S2 is performed with a gap underthe retainer ring 3, at which point the substrate carrier 10 is raised.The substrate carrier 10 is then again lowered (without moving it overthe scroll table 36B), and polishing from X2 to Y2 is performed with theretainer ring 3 pressed against the polishing surface 117A. The resultsobtained in the two procedures are essentially the same, but the processtime using Polishing Procedure (2) is shorter by as much time as itwould take to move the substrate carrier 10 to the scroll table 36B.

[0073] A Polishing Procedure (3) will now be explained with reference toFIG. 6, and when applicable, to FIG. 4. The procedure will be describedfor an example in which polishing performed using a fixed abrasive 15Bis followed by polishing performed with a polishing pad 15A. PolishingProcedure (3) is fundamentally the same as Polishing Procedure (1).

[0074] Unlike the apparatus of FIG. 1, the apparatus of FIG. 6 uses afixed abrasive 15B on the turntable 36A, and a polishing pad 15A on thescroll table 36B. The workpiece may be either a substrate Si as shown inFIG. 4(A), or a substrate S2 as shown in FIG. 4(B).

[0075] The following description would also apply for a substrate S2.That is, in the following text, ‘S2’ could be substituted for allinstances of ‘S1.’ The substrate S1 is secured on the substrate carrier10 by suction. The substrate carrier 10 is then moved over the turntable36A and lowered until the retainer ring 3 (FIG. 2) touches the fixedabrasive 15B. After the retainer ring 3 makes contact with the fixedabrasive 15B, the substrate carrier 10 is raised slightly to form a gapof prescribed size between the retainer ring 3 and the polishing surface17B of the fixed abrasive 15B. Next, polishing is performed, with thesubstrate S1 pressed against the fixed abrasive 15B. Since the initialpressing of the retainer ring 3 against a fixed abrasive 15B does notcause the “edge rounding” problem, it is not necessary, in this case, tokeep the retainer ring 3 pressed against the polishing surface 17B tosuppress rebound.

[0076] Because a gap of the prescribed size is formed between theretainer ring 3 and the polishing surface 17B of the fixed abrasive 15B,the entry of polishing solution between the to-be-polished substratesurface SA1 of the substrate S1 and the polishing surface 17A of thefixed abrasive 15B is improved, which increases the polishing rate.Because this also reduces retainer ring 3 wear, it greatly extends theservice life of the retainer ring 3.

[0077] When the prescribed amount of polishing has been performed; i.e.,when the to-be-polished substrate surface SA1 of the substrate S1 hasreached the X1 level (X2 if it is a substrate S2), this is detected bythe first end-point sensor mechanism 18, after which the substratecarrier 10 is raised, ending the polishing operation on turntable 36A.

[0078] Next, with the substrate S1 secured to the substrate carrier 10by suction, the substrate carrier 10 is moved to a position directlyabove the scroll table 36B, and then lowered until the retainer ring 3comes into contact with the polishing pad 15A. Then the substratecarrier 10 is lowered slightly, pressing the retainer ring 3 against thepolishing pad 15A. Polishing is then performed with the substrate S1pressed against the polishing pad 15A. This makes it possible to performuniform polishing to the edge of the substrate S1.

[0079] When the prescribed amount of polishing has been performed, assensed by the second end-point sensor mechanism 19; i.e., when theto-be-polished substrate surface SA1 has been polished down to the Y1level (or Y2 level in the case of a substrate S2) the substrate carrier10 is raised, ending the polishing operation on the scroll table 36B.The substrate carrier 10 is then moved over the pusher 30, to transferthe polished substrate S1 to the pusher 30.

[0080] Moreover, in Polishing Procedure (3), instead of performing thestep of polishing with a fixed abrasive 15B first, followed by the stepof polishing with a polishing pad 15A, the order of these steps may bereversed. Even when the order is reversed, however, polishing with apolishing pad 15A should still be performed with the retainer ring 3pressed against the polishing pad 15A, and polishing with a fixedabrasive 15B should still be performed with a prescribed gap formedbetween the retainer ring 3 and the fixed abrasive 15B.

[0081] In the above examples, a single substrate carrier was used toperform consecutive polishing processes using two different polishingtools 15. It should be obvious, however, that the present inventionwould also be useful for polishing performed using three or morepolishing tools 15. Moreover, the specific examples described abovedescribed only the polishing of metal films, but it should also beobvious that the present invention would also be useful for thepolishing of other films such as insulator films, or of STI (shallowtrench isolation) process. Also, the polishing apparatus 1 of thepresent invention is capable of supporting operations that require onlyone polishing tool 15, as well as those requiring multiple polishingtools 15. It is also capable of supporting operations in which pressingforce must be applied to the retainer ring 3, as well as those in whicha gap must be provided between the retainer ring 3 and the polishingsurface 17, with no requirement to apply pressing force to the retainerring 3. The present invention therefore provides a polishing apparatus 1and method for polishing that provide high substrate planarity, highpolishing rates, and high productivity, for support of a broad range ofpolishing applications.

[0082]FIG. 7 illustrates a polishing apparatus in accordance with afurther embodiment of the present invention. The polishing apparatus ofthis embodiment is different from those of the afore-mentionedembodiments with respect to their retainer-ring-position-adjustmentmechanism 4. That is, in the former apparatus, theretainer-ring-position-adjustment mechanism 4 is not provided and an aircylinder 120 is used as its actuator or a retainer-ring-pressingmechanism instead of the pulse motor 57 used in the latter apparatuses.

[0083] The retainer-ring-position-adjustment mechanism of thisembodiment is not able to position the retainer ring relative to thepolishing surface as precisely as that of the embodiment describedabove. In actuality, the mechanism of this embodiment effects adjustmentby applying an upward acting force on the retainer ring while keeping itin contact with the polishing surface. The force applied is onlysufficient to maintain contact between the retainer ring and thepolishing surface, to thereby enable a polishing solution to easily passbetween the retainer ring and the polishing surface and enter betweenthe substrate surface and the polishing surface, so as to provide anincreased polishing rate. Needless to say, it is also possible in thisembodiment for the retainer-ring-position-adjustment mechanism to spacethe retainer ring apart from the polishing surface, as is done in theembodiment described above.

[0084] In the present invention, as described above, aretainer-ring-pressing mechanism is provided for pressing the retainerring against a polishing surface. This eliminates the problem of ‘edgerounding’ in the polished surface, thus improving the substrate finishprecision. Also provided is a retainer-ring-position-adjustmentmechanism. When the substrate is pressed against the polishing surface,this mechanism makes it possible to adjust the positional relationshipbetween the retainer ring and polishing surface such as to form a gaptherebetween, or to make the retainer ring in slight contact with thepolishing surface. This lack of physical contact or a slight contactbetween the retainer ring and the polishing surface increases thepolishing rate (speed) thus improving polishing productivity.

1. A polishing apparatus comprising: a first polishing table, having afirst polishing surface; a substrate carrier for holding a substrate andpositioning the substrate so as to bring a surface of the substrate intocontact with the first polishing surface; a pressing mechanism forpressing, against the first polishing surface, the surface of thesubstrate which has been brought into contact with the first polishingsurface by the substrate carrier; a retainer ring mounted on thesubstrate carrier so as to surround the substrate which has been pressedagainst the first polishing surface by the pressing mechanism; and, aretainer-ring-position-adjustment mechanism for adjustably positioningthe retainer ring relative to the substrate, which has been pressedagainst the first polishing surface, in directions toward and away fromthe first polishing surface.
 2. A polishing apparatus as set forth inclaim 1, wherein the polishing apparatus further comprises a secondpolishing table which has a second polishing surface; the substratecarrier is capable of moving the substrate held by the carrier toselectively bring the substrate into contact with the first or secondpolishing surface; the pressing mechanism is capable of pressing,against the second polishing surface, the substrate which has beenbrought into contact with the second polishing surface; and, theretainer-ring-position-adjustment mechanism is capable of adjustablypositioning the retainer ring relative to the substrate, which has beenpressed against the second polishing surface, in directions toward andaway from the second polishing surface.
 3. A polishing apparatus as setforth in claim 2, wherein the first polishing surface is harder than thesecond polishing surface.
 4. A polishing apparatus as set forth in claim2, wherein the first polishing table has a fixed abrasive providedthereon and defining the first polishing surface; and, the secondpolishing table has a polishing pad provided thereon and defining thesecond polishing surface.
 5. A polishing apparatus as set forth in anyone of claims 2-4, wherein at least one of the first and secondpolishing tables comprises an end point sensor for sensing that thesubstrate pressed thereagainst has been polished by a prescribed amount.6. A polishing apparatus as set forth in claim 1, wherein the pressingmechanism comprises: a substrate-pressing member provided on asubstrate-holding side of the substrate carrier and defining aninflatable chamber between the substrate holding side and the substrateheld thereon; and, a pressurized fluid supply system for supplying apressurized fluid into the inflatable chamber; the retainer ring isfastened on the substrate carrier; and, theretainer-ring-position-adjustment mechanism is capable of adjustablypositioning the retainer ring relative to the substrate, which has beenpressed against the first polishing surface by the substrate-pressingmember due to an inflation of the inflatable chamber caused byintroducing the pressurized fluid into the inflatable chamber, indirections toward and away from the second polishing surface.
 7. Apolishing apparatus as set forth in any one of claims 2-6, wherein thepressing mechanism comprises: a pressing member provided on asubstrate-holding side of the substrate carrier and defining aninflatable chamber between the substrate holding side and the substrateheld thereon; and, a pressurized fluid supply system for supplying apressurized fluid into the inflatable chamber; the retainer ring isfastened on the substrate carrier; and, theretainer-ring-position-adjustment mechanism is capable of adjustablypositioning the retainer ring relative to the substrate, which has beenpressed against the first or second polishing surface by thesubstrate-pressing member due to an inflation of the inflatable chambercaused by introducing the pressurized fluid into the inflatable chamber,in directions toward and away from the second polishing surface.
 8. Apolishing apparatus as set forth in claim 6 or 7, wherein theretainer-ring-pressing mechanism comprises: a chucking plate positionedon and spaced away from a substrate-holding side of the substratecarrier; and, a resilient sheet connected between the peripheral edge ofthe chucking plate and the peripheral portion of the substrate carrierto define the inflatable chamber by the substrate-holding side of thesubstrate carrier, the chucking plate and the resilient sheet.
 9. Apolishing apparatus as set forth in claim 8, wherein theretainer-ring-pressing mechanism comprises: at least one resilientmember provided on a substrate holding side of the chucking plate onwhich a substrate is held, each resilient member defining an inflatablechamber between the substrate holding side of the shucking plate and thesubstrate; and, the pressurized fluid supply system supplies pressurizedfluid to the respective inflatable chambers independently.
 10. Apolishing method for polishing a substrate by pressing it against apolishing surface while surrounding the substrate by a retainer ring,comprising: a first step for subjecting the substrate and the polishingsurface to a relative slide motion in order to polish the substrateunder such a condition that the substrate is pressed against thepolishing surface while the retainer ring is spaced away from or inslight contact with the polishing surface; and, a second step forsubjecting the substrate and the polishing surface to a relative slidemotion in order to polish the substrate under such a condition that theretainer ring as well as the substrate are pressed against the polishingsurface.
 11. A polishing method as set forth in claim 10, wherein thepolishing surface used in the second step is harder than the polishingsurface used in the first step.
 12. A polishing method as set forth inclaim 11, wherein in the first step, a polishing pad is used to definethe polishing surface.
 13. A polishing method as set forth in claim 11or 12 wherein in the second step, a fixed abrasive is used to define thepolishing surface.
 14. A polishing method as set forth in any one ofclaims 11-13, further comprising: a third step for sensing that thesubstrate has been polished by a prescribed amount at least in the firstor second step.
 15. A polishing method as set forth in any one of claims10-14, wherein the second step is effected following the first step. 16.A polishing method as set forth in any one of claims 10-14, wherein thefirst step is effected following the second step.
 17. A polishing methodfor polishing a substrate by pressing it against a polishing surfacewhile surrounding the substrate by a retainer ring, comprising:polishing a substrate under such a condition that the substrate ispressed against a first polishing surface while a retainer ringsurrounding the substrate is spaced apart from the first polishingsurface; and, polishing the substrate under such a condition that theretainer ring as well as the substrate are pressed against the secondpolishing surface.
 18. A polishing method as set forth in claim 17,wherein the first polishing surface is harder than the second polishingsurface.
 19. A polishing method as set forth in claim 17, wherein thefirst polishing surface is made of a fixed abrasive and the secondpolishing surface is made of a polishing pad.